Wireless communication systems have become-ubiquitous in society. Consumers use a wide range of devices and networks, including cellular phones, paging devices, personal communication services (PCS) systems, and wireless data networks. Wireless service providers are creating new markets for wireless devices and expanding existing markets by making wireless devices and services cheaper and more reliable. Wireless service providers attract new customers by reducing infrastructure costs and operating costs, by increasing handset battery life, and improving quality of service, and new and better features.
Inadequate coverage is a persistent problem in the quality of service of any wireless network. Natural and man-made obstacles frequently create radio frequency (RF) “holes” in the coverage area of a wireless network. Voice and data call connections are frequently dropped when a wireless terminal, such as a cell phone or a similar mobile station, enters an RF hole. Mobile stations that are already in an RF hole may not be able to reliably establish new connections. Typical areas in which RF holes occur include underground tunnels, buildings that have large footprints, tall buildings, and underground shopping malls.
Wireless service providers may attempt to improve coverage and to eliminate RF holes by one or more conventional methods. A wireless service provider may use higher transmit power from the base transceiver station (BTS) to maintain communication with a mobile station (MS). However, the result is an increase in the noise floor experienced by other mobile stations in the coverage area of the serving BTS, leading to an overall increase in total BTS transmit power and a reduction in the percentage of transmit power available to support other calls.
Alternatively, a wireless service provider may attempt to improve coverage by installing another base transceiver system (BTS) in the area of poor coverage. A disadvantage of this method is the cost associated with acquisition and deployment of a complete base transceiver station. A typical full-service BTS may cost between $500,000 and $750,000. Adding another BTS also requires the added cost of provisioning a dedicated backhaul link to provide network connectivity. Still another disadvantage of adding a new BTS is that these devices are provider specific. Devices from two different vendors cannot be interchanged or operated in a given network.
Also, a wireless service provider may attempt to improve coverage by deploying RF repeater transceivers. Unfortunately, a repeater re-broadcasts the entire set of signals for all calls carried by the serving BTS, not just for those mobile stations in the poor coverage area. As a result, the mobile stations in the poor coverage area experience a higher noise floor. Thus, increased transmit power causes higher forward link transmit power per user channel on the serving BTS. In CDMA technology, the RF noise in the operating frequency is an important factor, especially in the forward link (i.e., transmission from BTS to MS). The repeater amplifiers add noise on both forward and reverse links. Thus, using repeaters degrades overall network performance by increasing noise in the environment and reduces the traffic capacity of the network.
Therefore, there is a need in the art for improved wireless networks having improved RF coverage. In particular, there is a need for an apparatus that can improve service in an area of poor RF coverage without significantly increasing transmit power in within the cell site or in neighboring cell sites.